temperature below 0° in a vessel or reservoir whose walls may be easily chilled, is always covered first on its surface by a thin stratum cf ice, and that afterwards the walls and bottom of the vessel also become covered with a stratum of ice. II. The thickness of this stratum is in direct ratio to the intensity of the cold, and in inverse ratio to the conductibility of the walls; the stratum of ice itself operates as a wall, which is a bad conductor. III. There remains, almost always, at the centre a certain quantity of water which, surrounded on every part by ice, with difficulty loses its latent heat, and does not freeze. Very often, also, a bubble of air, which has been disengaged from the water during its congelation, is comprised in the mass. But it sometimes happens, through intense and continued cold, that the upper ice cracks, and the caloric of the central mass escaping by the fissures, the whole congeals, and the surface assumes a convex and protuberant form, from the expansion of the ice formed at the centre. IV. The plashes or small puddles of water which occur in the roads or fields are promptly covered with a thin crust of ice, which assumes the form of films crossing each other at 30, 60, and 120 degrees, and leaving void spaces between them; the water which filled them is absorbed by the porosity and capillarity of the surrounding earth, and, in turn, becomes congealed. V. It is quite otherwise with water in large masses, for water at 4°.44, being specifically heavier than that at 0°, descends to the bottom, while the water of the surface continues to grow colder, and finally is frozen. VI. In order, then, that ice may be formed at the bottom of great masses of water, it is necessary, first, that the water should be impressed with a movement sufficiently rapid to overcome the superposition by strata according to the differences of specific gravity, and to bring to the bottom the cold strata, so that the water may be chilled to 0° quite to the bottom and the inferior walls, growing progressively colder, shall also be brought to 0°; secondly, that there shall exist in the midst of the current an obstacle against which the water impinges.

In effect, whenever there occurs in a current a body forming an obstacle, the collision with that obstacle augments the movement of rotation of the current, and may even occasion a vortex or eddy in the water; it must be recollected at the same time that behind this obstacle there is a space where the water is in a state of perfect repose-so much so that when the body which forms the obstacle is of considerable volume, a deposit of sand and even pebbles takes place at that point and forms a sort of delta. It is here that the ice of the bottom, the grundeis, is formed, the adhesion of which gradually augments the volume of the obstacle and the effect produced, until the moment when, by virtue of its smaller specific gravity, the ice is detached, and is borne to the surface of the water.

At a session of the Society of Natural History of Strasbourg, May 3, 1864, Professor Bertin presented a memoir on the polarization of light by ice, from which it appears that the ice formed at the bottom of water polarizes light in the same manner as the ice formed at the surface.

There is a valuable article on ice, by L. F. Koemtz, in the Encyclopædie of Ersch and Gruber. The specific gravity of ice is there given as follows: According to Kraft, 0.905; Irwin, 0.937; Scoresby, 0.9146, 0.9166, 0.9253; Royer and Dumas, 0.950; Osonn, 0.9268. Thomson, in his Chemistry, gives 0.2900, which is nearly the mean of the above numbers.

As regards the form of the crystal of ice, Haüy thought that it might be deduced from the octahedron. Brewster (Poggendorff's Annalen, t. vii, 509) recognizes hexahedrons terminated by three planes. Hericart de Thury (Ann. de Chimie et Physique, xxi, 156) adopts the hexahedral prism. Clarke, (Trans. of. the Philosophical Society of Cambridge, 1213,) in a seemingly very exact article, pronounces for rhombohedrons, with angles of 120 and 60 degrees. This is confirmed by Marx and Brewster, (Ann. de Poggendorf, xxxii, 399,) and seems corroborated by our own observation of lines crossed at 30, 60, and 120 degrees, as already noticed. See also Scoresby: Cristillisation de la neige, in the Ann. de la Chimie et de Physique, t. xviii.

THE EARTHQUAKE IN EASTERN MEXICO OF THE

SECOND OF JANUARY, 1866.

BY DR. CHARLES SARTORIUS, OF MIRADOR, NEAR HUATASCO, DISTRICT OF CORDOVA, STATE OF VERA CRUZ, MEXICO.

[From a letter addressed to the Smithsonian Institution.]

On the 2d of January, 1866, at six hours ten minutes in the evening, the earth shook without detonations; the movement seemed to be vertical, and lasted some ten seconds; then followed a strong shock from west to east; after eight seconds another equally strong, succeeded by strong oscillations which endured for about twenty seconds, and finally subsided in a tremulous motion. The du ration of the whole phenomenon I estimated here at one minute. The beams of houses creaked and were perceptibly moved; doors opened and closed; utensils were thrown down from west to east; mirrors and pictures on the wall shook to and fro; and a pendulum, which I had suspended by a long string, exhibited vibrations of one yard for ten minutes after the whole was over. The column of the barometer sank and rose-the magnetic needle vibrated. These were the phenomena here, but no walls were fractured, and the high chimneys of the steam and sugar factories remained uninjured. The hills consist throughout of conglomerates, which may be observed in ravines to the depth of 500 feet.

Huatasco lies about ten miles (English) south from this place, surrounded by volcanic hills, (trachite and lava,) in a southwardly direction from which project three mountain craters, composed of crystalline limestone. Here the effects were much stronger. In the cathedral a part of the dome fell in; the walls of many houses were ruptured; hundreds of earthen and porcelain vessels were dashed to pieces. In two neighboring villages the churches were destroyed, and large masses of rock were detached in the adjacent limestone mountains and rolled into the valley.

The focus and centre of the whole concussion was the volcano of Orizava, which rises ten miles southwestwardly from Huatasco. At its foot, on the east side, lies the city of Coscomatepec, of 4,000 inhabitants. Here the concussion was so violent that the new and strongly-built parish church, with cupola and trebly vaulted dome, was reduced to ruins; many private houses were rendered uninhabitable; many walls overthrown, but no human life was lost. On the west side of the great mountain, the city of St. Andres Chalchicomula suffered more than any other; several churches and numerous houses were destroyed, and many of the inhabitants buried under the ruins.

The history of the country informs us that the volcano was in activity from 1559 to 1569, but has since been at rest. Yet, although eruptions may have ceased, certain it is that the flame in its depths has not been quenched. This is manifested by the columns of smoke which ascend from time to time, the f marolles on the sides, glowing hot rocks on the western declivity, hot sulphu rous springs at the eastern foot, &c. On the morning after the earthquake it was observed that the snow-covered cone (3,000 feet, the absolute height of the mountain being 17,800 feet) was almost bare of snow on the south side, while the southwest border of the crater had fallen and a vertical cleft of the highest peak had taken place. This cleft traversed the entire summit, and from its

deepest part gushed great volumes of water. The length of the cleft is estimated at 1,000 metres; its breadth at one metre. The volcano is surrounded by limestone mountains, and stretches southwardly in a calcareous formation. Wherever limestone forms the chief mass of the chain, the effect of the concussion was greatest. In the village of Chocaman, on the southeast side of the volcano, between high calcareous ranges, under which extends a stratum of clay slate, the violence of the concussion is most conspicuous. The church built in the sixteenth century fell, but of the three stories of which the tower consisted, the middle one was precipitated outward, so that the highest fell upon the lowest, and remained standing.

In the city of Cordova the church of the convent of San Antonio, two hundred years old, sustained the loss of its cupola and the dome of its nave, while the parish church-a handsome building with three vaulted naves-is so injured as to be unfit for divine worship; the large town hall, with its arcades, the hospital, and many private dwellings were likewise so much damaged as to threaten to fall.

Orizava, eight miles west from Cordova, though surrounded by high calcareous ridges, suffered less; the reason of which may be that the town stands on the site of an ancient lake, which, after a bed of from six to eight feet of damearth, contains a thick stratum of chalk, and from its porosity propagated the shock with less force; yet damage was not wholly averted. A church once

belonging to the Jesuits was thrown down, as was also the upper part of the high tower of the cathedral. This part had been but newly built, in order to place a clock thereon, when the earthquake of October, 1864, hurled it thirty yards distant towards the market-house; the reconstruction was resumed, and on the day when the clock was placed in position the earthquake again demolished the dome of the tower, but without injury to the clock.

From Orizava a valley stretches to the southwest, bordered by steep rocks, through which passes the highway leading to Mexico. In this valley, which is twelve miles long, the concussions were peculiarly violent. Several churches and many private houses were destroyed, and a number of persons lost their lives. Further to the south the towns of Tehuacan and Oajaca were visited most severely; in the latter five churches were wholly or in part demolished. From the report of a traveller the force of the shocks, in the long distance from Orizava to Oajaca, was peculiar, the effects being rather extended in length than diffused in breadth. The neighborhood of the calcareous mountains, which run parallel to the great chain of the Andes, would seem to have determined the conditions of the concussions.

Northward from the peak of Orizava, it was only quite near that point that the movement was violent; here a church was destroyed. In Jalapa, though very perceptible, the phenomenon was attended with no damage. The same was the case to the east, as, for instance, at Vera Cruz. A strong norther was blowing at the time, on which account the effects were not perceived on board the ships in the harbor.

'To the westward the oscillations were slighter according to the greater distance from the peak of Orizava. In Puebla the concussions were strong, but not so much so that large buildings were injured. In the city of Mexico the effects were mitigated. According to a communication from a point seventy-two miles west of the latter city, an earthquake, but of no considerable force, was distin guishable.

All opinions concur in assigning the peak of Orizava as the focus of the phenomenon, as it was also in October, 1864, and it would not be surprising if that mountain, after a repose of three hundred years, should again commence its eruptions.

NOTE. The following supplementary communication was received from Dr. Sartorius, in a letter of the 27th May, 1866:

"We had another earthquake at 9.15 a. m. of May 10, 1866, extending from the peak of Orizava in a direction from southwest to northeast. There were three shocks, at intervals of ten seconds, the last the most severe, followed by continued tremblings; the duration of the whole was seventy seconds, during which the barometer fell one-hundredth of an inch, returning immediately after to its original condition. The magnetic needle was without declination, but with a strong inclination north. The earthquake was local, only feeble traces having been observed in the city of Mexico. The shock was so severe in Orizava thai several houses were destroyed and some persons killed. The oscillations were from north to south; the time the same.

66

On the 27th of April a violent shock was noticed southwest of the city of Mexico, proceeding from the volcano of Jorullo, of which no traces were observed here."

STATISTICS RELATIVE TO NORWEGIAN MOUNTAINS, LAKES, AND THE SNOW-LINE.

DEPARTMENT OF STATE, Washington, November 22, 1865.

SIR: I transmit herewith, for your information, and the use of the Institution, a collection of tables, maps, &c., showing the height of the Norwegian mountains, with other valuable papers transmitted to this department by the consul of the United States at Bergen as enclosures in his despatch No. 52, dated September 29, ultimo.

I will thank you to advise this department of the receipt of the same.
I am, sir, your obedient servant,

JOSEPH HENRY, Esq.,

Secretary of the Smithsonian Institution.

F. W. SEWARD,
Assistant Secretary.

STATISTICS OF NORWEGIAN MOUNTAINS EXCEEDING THREE THOUSAND FEET IN HEIGHT.

In the geographical publications relative to Norway published in foreign countries, the heights of few of its mountains have been given, and even of those few, the statements with regard to many are erroneous. I have therefore deemed it expedient to compile a table of those Norwegian mountains which exceed in height 3,000 feet above the level of the sea. The measurements in all cases have been reduced to English feet, the Norwegian foot being equal to 1.029357 English; all fractions under half a foot have been stricken out, and all over half counted as one.

The measurements made by theodolite, levelling, or other geometrical methods are specified; all others were obtained by the barometer. I have given all the different measurements and results made by different persons, and it will be observed that many of these measurements, made at different times, differ considerably. Such discrepancies are due to the state of the atmosphere and forbid perfect confidence in the results, but great heights cannot well be measured by levelling or other geometrical methods without involving much time and great expense. It is, however, thought that when measurements are made on different days, the mean result will be nearly correct.

The length and breadth of the larger lakes of Norway stated herein are derived from Mr. Schöth's Geography, in which the dimensions are given in Norwegian miles, all fractions below one-sixteenth of a mile being rejected. The dimensions are reduced to English geographical miles, the proportion adopted being one Norwegian mile to six English geographical miles. There are, in addition to the lakes whose sizes are here given, many smaller, but, as it was only my intention to furnish a correct enumeration of the larger ones, as of the highest mountains, all less than one Norwegian mile in length have been left unnoticed, as being of inferior interest.

I have also given the height of the snow line indicated by different observers, from which it will be seen that the gradual descent of this line toward the